text: Channelization of a stream may be undertaken for several reasons. One is to make a stream more suitable for navigation or for navigation by larger vessels with deep draughts. Another is to restrict water to a certain area of a stream's natural bottom lands so that the bulk of such lands can be made available for agriculture. A third reason is flood control, with the idea of giving a stream a sufficiently large and deep channel so that flooding beyond those limits will be minimal or nonexistent, at least on a routine basis. One major reason is to reduce natural erosion; as a natural waterway curves back and forth, it usually deposits sand and gravel on the inside of the corners where the water flows slowly, and cuts sand, gravel, subsoil, and precious topsoil from the outside corners where it flows rapidly due to a change in direction. Unlike sand and gravel, the topsoil that is eroded does not get deposited on the inside of the next corner of the river. It simply washes away.